The present invention is directed to an internal valve for use in a mobile tank car for locking the valve in a closed position to provide a positive seal, a fire safe valve and prevent spillage of the material inside of the tank in the event of an accident. Additionally, the valve of the present invention may provide a secondary seal.
It is known as described in U.S. Pat. No. 5,042,776 to provide a valve that can be used for loading or unloading mobile tanks, such as railroad tank cars or tank trucks or other types of tanks handling liquids, gases or slurries. Such a valve is positioned internally of the tank and therefore is less subject to being damaged. Such an internal valve may be conveniently installed from the exterior, easily removed for repair or replacement.
However, railroad tank cars and truck tanks are notoriously subjected to vibrations and shocks. In order to increase the safety factor the present invention provides an internal tank valve having a primary seal which can be more securely locked in the closed position to assure a positive seal, a fire safe valve, and reduce the likelihood of spillage of material from inside of the tank in the event of a derailment or accident of the tank car. And of course such locking structure must be provided at a location where it is less likely to be damaged.